This invention relates, in general, to a high pressure tanks and safety valves therefor and relates, more particularly, to a high pressure tank containing contents under pressure and which is which is plugged by a broken safety valve of a special type.
The type of high pressure tank with which this invention is concerned defines a circular throat opening adapted to sealingly receive a portion of a safety and/or service valve through which the tank is emptied and filled and includes an externally-threaded annular flange positioned about the circular opening of the tank and normally provided for the attachment of a valve-protector cap. Such containers are commonly in the form of thick-walled cylinders and the aforesaid annular flange is commonly an integral extension of the tank cylinder. An example of a tank of the aforedescribed type is shown and described in U.S. Pat. No. 4,077,422.
The type of safety valve with which this invention is concerned includes a body having a sealing portion for closing the circular opening in a tank and an external portion defining a valve outlet port. The sealing portion defines an inlet port positionable internally of the tank, and a flow passage extends between the valve inlet and outlet ports. Defined within the portion of the flow passage positioned internally of the tank is a ball chamber having an inlet end and an outlet end, and a spherical ball is loosely received by the ball chamber and adapted to be biased into sealingly engagement with the outlet end thereof when the fluid pressure at the ball chamber inlet end is higher than that at the ball chamber outlet end. The valve further includes means associated with the external portion of the valve body for preventing the ball from engaging the ball chamber outlet end until the external portion is separated from the sealing portion. If the external portion of the valve is broken away from the sealing portion, the pressure of the tank contents seats the ball in the ball chamber outlet end and thereby prevents the escape of the tank contents. Such a valve is shown and described in pending application Ser. No. 642,201, now U.S. Pat. No. 4,562,852, entitled SAFETY VALVE and having the same inventor as the present invention.
Because a valve such as is described in the referenced pending application is known to prevent the sudden escape of contents of a high pressure tank if the external portion of the valve away from the valve sealing portion, the valve is desirable for safety considerations. If, for example, the external portion of the valve is broken off, the valve ball and associated chamber prevent the tank from becoming a dangerous and destructive projectile. However, before the high pressure tank is rendered operational or can be returned to service, the pressure in the tank must be relieved and the valve sealing portion removed. Therefore, there exists a need for means by which the pressure within such a high pressure tank can be relieved.
It is, accordingly, an object of the present invention to provide an apparatus and method for relieving the pressure within a high pressure tank plugged by a portion of a broken safety valve of the aforedescribed type.
Another object of the present invention is to provide such an apparatus and method wherein the contents of the high pressure tank can be salvaged or reclaimed.
Still another object of the present invention is to provide such an apparatus which is uncomplicated in structure and economical to manufacture.
Yet still another object of the present invention is to provide such an apparatus which is safe and dependable in operation and easy to use.